- The declining water temperature with depth behind the dam- equivalenthead of the theoretical height of the dam assuming you are using the storedenergy and temperature difference of the smaller dam

Thermocline energy using a heat engine

h(m)= (C changeT2/gTH) = (CchangeT/g)(ChangeT/TH)f

- (changeT/TH) = second law tolls- f = engineering imperfections

h(m) = the equivalent height of a theoretical dam that has the same potential energy as the accessible thermal energy in the actual dam, where "accessibility" takes into account second law tolls and engineering imperfections

First Law Efficiency

n = (energy delivered by a system)/(energy supplied to the system

-emphasize quantity-device oriented-n>1 is called Coefficient of Performance "COP"

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First Law Efficiency with regards to heat pumps (assuming 1st law is COP)

It is impossible to have a perfect heat engine; a perfect heat engine is a perpetual motion machine of the second kind

DRAW HEAT ENGINE/HEAT PUMP ON TEST

2nd law tolls

- 2ndlaw tolls are specified by the Carnot engine since it produces no entropy.These tolls exist to satisfy the 2ndlaw of thermodynamics.Waste heat from aCarnot engine consists only of 2nd law toll-Underidentical temperature conditions, a real heat engine will always produce morewaste heat than a Carnot engine.Thisadditional waste heat originates from the engine’s engineering imperfections

Thermocline energy vs exergy

-thermocline energy =

oMgh = MC(change)T

oh(m) = (C/g) (change)T = 427 (change)T

-thermocline exergy =

oMgh = MC(change)T x (change T/T) x f

heat energy efficiency

-N = work out/heat input-N = W/Qh = f[(change)T/Th]

Combined cycle

oFirst stage is a gas turbine – the air thatcomes out is suuuper hot though, which is used in the second stage to makesteam

oSecond stage is a steam turbine

oEssentially, this ends up making electricitytwice

Combined heat and power

oThere has to be a cold place to condense thesteam to make the turbine go round.Thecold place is usually a cooling tower or river

oSimultaneous use of electricity and waste heatis Combined Heat and Power “CHP” or co generation.

matching energy grade with use saves energy and preserves the environment; 2nd law efficiency is a measure of how well this matching is accomplished

the nuclear situation

1.Almost all recoverable uranium is in theoceans.

2.No-one has yet demonstrateduranium-extraction from seawater on an industrial scale.

3.To get off fossil fuels by using nuclear(once-through fuel cycle) nuclear must increase 40 times.

nuclear situation continued

1.To do 1/3 of this from fissioningseawater (about 10TW by 2050) requires a flow through hypothetical collectorsin the sea equal to 10 times than the outflow of all the worlds rivers.

2.Nuclear reactors have been proposed asthe only serious contender to avoid carbon emissions.Known uranium supplies are insufficient to dothis using once-through reactors. This fact argues for uranium and thorium breeders.

3.Today the world has 435 operatingreactors (France has 59, & has US 103)

Components of Fission LWR reactors: 5 parts

fuelmoderatorcontrol rodsshieldingcoolant

NUCLEAR REACTOR STUFF TO KNOW FOR TEST

Fukushima, it's containment building, and shielding

also know 5 parts of the reactor

Components of Fission LWR reactors: fuel

use fissile nuclei arrange in a low density and with 235U92 enriched to about 4.5% from 0.7%

light water (LWR), heavy water or graphite; requirements: negative temperature coefficient and must not absorb neutrons

Components of Fission LWR reactors: control rods

neutron-absorbing material: cadmium or boron

Components of Fission LWR reactors: shielding

keep radioactivity out of the biosphere i.e. defense in depth

Components of Fission LWR reactors: coolant

water, helium; requirement: must not absorb neutrons

Nuclear reactor FWR: fuel continued

A. Enrichmentby isotope separation (235U and 238U)1.Lasers2.CentrifugesB. Fuel reprocessing*1.235U that remains in spent fuel (about 0.7% after one year).2. 239Pu that was produced by accidentalbreeding.C.Fissilefueldensity: keep it low

D. Weapon proliferation resistance

Breeder reactor

the fertile to fissile conversion rate is greater than the consumption rate of the fissile nuclei